Examination of heat-induced milk proteins gel structures by the small angle X-rays scattering (SAXS) method.

The small angle X-rays scattering (SAXS) method was applied to examine the protein gel structures of bovine serum albumin (BSA) and whey protein isolates (WPI). This method facilitated the determination of various forms of protein gel structures and their fractal dimensions depending on the pH, concentration and the kind of protein. The SAXS curves of different BSA and WPI gel structures were versatilely analysed according to Porod - Soule dependence by fulfilling the power law scattering requirements. The fractal dimensions of individual gel structures and their structures and their standard deviations from the power law scattering were estimated. It was confirmed that the fractal dimensions of a given protein origin had similar structure, but for a different proteins, they formed varied structure. The formation of different protein gel structures depended on pH values and this was confirmed by SAXS curve appearances and fractal dimensions. Analysis of the obtained SAXS data, showed a more complicated structures in WPI protein gels than in the BSA ones. Furthermore, the WPI gel structures were more unfolded than the BSA gels. This work showed all possible interpretations of SAXS curve for protein gels based on the current theory of the SAXS method.